1. Field of the Invention
The present invention relates generally to the modular construction industry, and relates more specifically to a construction system for manufactured housing units, which units can form multi-story structures at a building site.
2. Description of Related Art
The conventional building construction art for years has recognized the cost and efficiency advantages of having construction in most part completed at the manufacturing plant, as opposed to significant construction on-site. xe2x80x9cManufactured housingxe2x80x9d as used herein means a virtually complete and finished housing unit, wherein a significant portion of the construction of the unit is completed at the manufacturing plant. In current construction techniques, manufactured housing includes, for example, mobile homes that are built in most part at the factory. The interior partitions, doors, fixtures, equipment, windows, among others, are installed in the mobile home before it leaves the plant. Manufactured housing thus is not meant to include simply modular core constructions with little to no finishing that are shipped to a construction site for finishing and integration into a building structure.
Manufactured housing fills a tremendous need for affordable, single-family housing in rural areas of the country. In fact, manufactured housing accounts for approximately one-third of the total housing starts over the last several years.
Specific advantages and limitations of prior art building construction techniques follows. A first set of points outlines many advantages of manufactured housing, vis-à-vis on-site construction. Conversely, a second set of points illustrates construction applications where onsite construction is preferred over manufactured housing techniques. Typically, a building structure comprises only one of these two types of construction techniques; they are often mutually exclusive. For example, multi-story structures comprises almost exclusively of on-site construction elements. While it is undisputed that costs would be lower and construction efficiencies increased if multi-story structures could comprise in significant portions manufactured housing, the current state of the manufactured housing art does not enable such construction.
Thus, a third set of points are discussed that particularly identify the current limitations and roadblocks of utilizing manufactured housing units in a multi-story structure, as opposed to simply cornering manufactured housing techniques for only single-story modular structures. It is the specific prior art deficiencies of this third set that the present invention primarily addresses and overcomes, such that multi-story structures can indeed comprise in significant portions manufactured housing.
A. Benefits of Manufactured Housing
Manufactured housing as embodied in, for example, the present manufacture of mobile homes offers several advantages over site-built housing construction. In the factory environment:
Construction can occur year round, regardless of the weather.
Production in the factory with the use of jigs and assembly line techniques leads to a more uniform product under quality control supervision.
Assembly line efficiencies enable one man to do more than one task.
Completion time for construction is reduced.
Typical factory wages are substantially less than field wages.
Units are almost fully pre-finished in the factory, so that interior partitions, doors, fixtures, equipment and windows, among others, are installed in the units at the factory.
Site setup requirements are reduced since the modules are shipped with most of siding, roofing and interior finishes complete.
It is clear from the above non-inclusive list of advantages that generally the more construction carried out at the manufacturing floor, the better. Yet, present manufactured housing has its limitations.
B. Benefits of On-Site Construction
Site-built construction conventionally is preferred over manufactured housing for multistory structures. Several reasons for this include:
Flexibility in design without being restricted to the use of xe2x80x9crectangularxe2x80x9d rooms or sections.
Compliance with current building and life-safety codes that typically require the use of materials such as concrete and steel that are stronger and less flammable than wood, and thus more expensive and time consuming to ship to the site as complete.
The perception that manufactured housing as it relates to multi-story structures is simply xe2x80x9cstack-a-shackxe2x80x9d construction.
C. Limitations of Manufactured Housing with Multi-Story Structures
It is known only in some very specific and limited applications to use manufactured housing elements in a multi-story structure. Yet only a very few of the advantages attributable to manufactured housing reside in these limited applications:
Each manufactured housing unit is typically built with a separate floor and ceiling. Thus, when stacking units one atop another at the site, the floor on an upper unit is set upon the ceiling of a lower unit. This results in a redundant doubling of the number of structural joist members. This is unlike conventional on-site construction that uses the same joist members for both the upper floor and the lower ceiling between two modules.
According to most building and life-safety codes, it is prohibited from building wood structures over three stories in height. For a building to have more than three stories, steel or concrete structural members typically must be used. This additional building height requires supporting structural members in a diversity of sizes. For example, the lower floors typically require wider vertical members with varying spacing. Concerns about the weight, shear, and wind loads as more floors are added put even greater emphasis on the positioning of the exterior load bearing walls, thus reducing the flexibility in floor plan design.
The use of concrete for a manufactured housing unit""s walls and floors necessitates time-consuming form preparation with more complicated handling considerations. Typically, the units are smaller, thus requiring several units per floor in a building. This increases transportation costs along with the need for more material per floor.
Steel is easier than concrete to use in a manufacturing plant. The art is well developed in the use of steel for building multi-story structures. However, the typical assembly techniques utilizing steel have limited the amount of the manufactured housing unit""s interior and exterior finish that can be completed in the factory. For example, the art has heretofore relied heavily on welding to connect most of the structural steel elements that are required in a multi-story building. Welding units together on-site is very cumbersome and can generate heat and sparks that can easily damage any factory-constructed interior or exterior finish that is near the joint to be welded. Thus, truly finished manufactured housing units cannot be used in such building techniques.
A major portion of the construction of a modular-built, multi-level structure still is completed at the site. Most of the exterior finish is not completed until the manufactured housing units are set because of the access required by men and machine to attach the units together, both horizontally and vertically, which access would destroy a factory-constructed exterior finish.
Multi-story modular buildings are typically erected by first setting the manufactured housing units in place both horizontally and vertically, and then building and attaching connecting breezeways, corridors and stairs. This progression of setting the units first prior to breezeways, corridors and stairs) creates its own four distinct problems.
(1) The more units that are used (especially the higher the units are stacked), the more difficult it is to keep each subsequently higher unit level and plumb.
(2) For buildings exceeding two floors, it is very difficult to maneuver each unit into place at the site. Although a crane can come close to setting a module fairly accurately on top of another module, it typically requires construction workers around the perimeter of the module to pull, push and adjust the alignment of the upper module, which can further compromise the exterior finish of a unit.
(3) Beyond two stories, it becomes very difficult just to get workers to the necessary exterior surfaces to attach the units to each other.
(4) Because the connecting corridors and stairs are erected after the units are set, the exterior sides of the modules that abut the halls and stairs can not be finished in the plant because of the potential for damage as the stairs and corridors are built on site, thus necessitating more on-site construction.
These problems effectively negate the savings and efficiencies realized with construction in a manufacturing plant.
Prior Art References
Several designs for floor/ceiling units are disclosed representatively in U.S. Pat. Nos. 1,886,962, 3,510,997, 3,724,141, 4,211,043 and 5,575,119. Each of these designs are basically hybrid panelized construction methods; that is, the floor of an upper unit functions as the ceiling for a lower unit just as conventional on-site construction builds multi-story structures. One can go to any construction site where a multi-floor complex is being built and watch as one floor is built over another over another. Yet, in such prior art designs, the floors and ceilings of the manufactured housing units are not substantially finished at the factory, but on-site. Thus, these conventional panel assemblies still require extensive finishing at the site, including wall and ceiling finishes, floor coverings and installation of cabinets and fixtures. Further, a majority of these panels are built from concrete, a very difficult material to use for mass production.
Conceptually, a major portion of U.S. Pat. No. 4,202,339 to Fisher addresses the prior art problems of the redundancy of materials in a floor/ceiling combination. Fisher addresses the redundancy of materials by proposing the use of xe2x80x9cU-shapedxe2x80x9d and xe2x80x9cTubularxe2x80x9d modules that are to be stacked. Theoretically, where a xe2x80x9cU-shapedxe2x80x9d module is stacked upon another xe2x80x9cU-shapedxe2x80x9d module, the horizontal portion of the upper xe2x80x9cUxe2x80x9d acts as a ceiling for the lower xe2x80x9cUxe2x80x9d.
However, because the modules are presumably shipped to the site on standard flatbed carriers, the ceiling portion of the upper xe2x80x9cUxe2x80x9d can not be finished, for example, painted or stippled, until after the modules are erected on site. Accordingly, since the ceiling needs to be finished at the site, the degree of factory finishing of the walls, floors and fixtures is limited because of the potential damage to these areas while the ceilings are being shipped and completed. Although this proposed modular construction method theoretically eliminates the redundancy of wall and floor/ceiling materials, it does very little to take advantage of the pre-finishing opportunities that factory construction offers.
Fisher provides no details regarding the make up of the xe2x80x9cfloorxe2x80x9d (the horizontal section) of each xe2x80x9cU-shapedxe2x80x9d module. Further, the reference is silent as to how the pre-finished xe2x80x9cU-shapedxe2x80x9d module can be shipped other than xe2x80x9cit can be braced during transportationxe2x80x9d. Regarding the amount of factory work, or pre-finishing, possible with this design, Fisher broadly notes that xe2x80x9cthe modules are pre-finished as much as possible in the factory; exactly how much depends upon the specific manufacturerxe2x80x9d. Lastly, Fisher is similarly limited when it comes to the types of pre-finishing that can be completed at the factory as the xe2x80x9ctube-shaped module 34 is pre-finished with a textured surface or other desired surface to form the ceiling for the room beneathxe2x80x9d, yet provides no specific examples on how this could be done. For example, how could such a pre-finished surface be shipped without sustaining damage during shipping? How could such a pre-finished surface be erected at site without sustaining damage while being placed into the proper alignment?
It thus can be seen that a need yet exists for a floor/ceiling assembly that avoids the redundancy of materials for prior art floors and ceilings of stacked units, and enables finishing of the assembly at the plant, rather than on-site.
The success of manufactured housing construction also is limited in view of the prior art deficiencies in providing adequate load-bearing systems that can accommodate the load pressures of stacked units. Typically, the walls of the unit must be significantly thick so as to bear the weight of the structure, or obtrusive exterior or interior load-bearing pillars must be used in connection with panels of the module. Yet, significantly thick walls on manufactured housing units would lead to soaring transportation costs, while load-bearing pillars are unsightly.
Prior art references disclose the use of vertical steel tubing in combination with the units to provide the load-bearing capacity. U.S. Pat. Nos. 3,925,679 and 4,592,175 disclose tubing assemblies that primarily act as reinforcing agents in the walls of the unit. U.S. Pat. Nos. 3,927,498 and 5,755,062 disclose building techniques wherein the tubes basically are used as framework to which wall and floor panels are attached. U.S. Pat. No. 4,470,227 makes use of angle iron only as temporary exterior bracing.
U.S. Pat. Nos. 4,723,381 and 5,528,866 propose the use of exposed vertical structural steel members for the exterior support of the assemblies. Yet such a method of construction is contrary to manufactured housing as the proposed external supports lack the practical considerations of aesthetics, exposure to the elements, and code restrictions.
It thus can be seen that a need yet exists for a load-bearing assembly that can accommodate the load pressures of stacked units, thus freeing the exterior walls from a majority of this support.
Present interconnection techniques between adjacent modules utilize welding. Welding is used to connect most of the structural steel elements that are required in a multi-story building. Yet, welding is very cumbersome and generates heat and sparks that can easily damage any finish that is near the joint to be welded, nearly eliminating the capability of using fully-finished modular units in a multi-story structure. U.S. Pat. No. 3,927,498 illustrates the prefabricated panels being fastened to the vertical support tubes with bolts, but the bolts are exposed to the interior of the structure. Further, the bolts can not act as assembly guides because they are not fixed in position, nor are they used for the purpose of interconnecting independent structures.
U.S. Pat. No. 4,592,175 also discloses the use of bolts to connect the stacked modules both horizontally and vertically. The connection of one unit on top of another is accomplished by aligning pre-drilled holes in the base channel for the top unit to the holes in the rear plate on the bottom unit. Horizontally, xe2x80x9cside platesxe2x80x9d with pre-drilled holes are welded to the floor channels that are bolted together as the channels abut. These connections are made from the exterior of the module. The connections then need to be covered (hidden) by applying xe2x80x9cany desired facadexe2x80x9d at the site.
U.S. Pat. No. 5,761,862 relates to the construction of buildings using xe2x80x9cpre-formed concrete sectionsxe2x80x9d. This is basically a panelized system using concrete sections. The walls, floors and roofs are slabs that are put together at the site. There are primarily two types of connections. One is a vertical connection for two wall sections, and the other is a rod placed into holes that align the walls vertically on top of each other. None of the surfaces are pre-finished, and as with any panel system, no fixtures are pre-installed.
It thus can be seen that a need yet exists for an interconnection assembly to connect the units at the site, which interconnection assembly does not inhibit the pre-finishing of all of the interior and exterior walls.
There exists prior art attempting to overcome the disadvantages associated with multistory modular construction, wherein the modules are first set in place both horizontally and vertically, and then connecting breezeways, corridors and stairs are built around them. This progression of setting the modules first presents stabilization problems. U.S. Pat. No. 3,830,026 relates to a staircase that is xe2x80x9cfabricated only from a relatively small number of pre-cast or pre-formed substantially planar slabs and a plurality of pre-formed stairways having risers and treadsxe2x80x9d. U.S. Pat. No. 3,927,518 discloses prefabricated stairs for multi-story buildings. Neither of these references teach or suggest a complete core assembly that includes the stairs in addition to, for example, the hallways, utility rooms and elevator shafts. An additional limitation of the above staircases is that the construction of the main building will still require the use of some scaffolding and ladders, wherein a complete core assembly could eliminate such expense and time.
Therefore, it can be seen that a need yet exists for a stabilization assembly that provides a way to effect the erection of the units without damaging the pre-finished units. It can further be seen that a need certainly exists for a manufactured housing unit construction system capable of providing solutions to the above-identified problems of conventional multi-story modular construction. It is to such a construction system that the present invention is primarily directed.
Briefly described, in its preferred form, the present invention provides interrelated embodiments of a construction system for a multi-story structure comprising manufactured housing units that enables the finishing and completion of considerably more of the housing unit at the manufacturing plant (as opposed to on-site construction) than is presently available. A housing unit may refer to a permanent housing structure such as condominiums and apartments, and more temporary housing like motels and hotels.
The present invention discloses construction techniques for xe2x80x9cmanufactured housing unitsxe2x80x9d so as to distinguish the present xe2x80x9cunitsxe2x80x9d from the rather broad term xe2x80x9cmodulesxe2x80x9d as used in the art. xe2x80x9cModulexe2x80x9d is used in the art to denote any standardized unit of measurement, and thus open to numerous interpretations. For example, the present manufactured housing units are distinguishable from xe2x80x9cmodular utility core unitsxe2x80x9d that are well known and have been used in hybrid site construction for years. The manufactured housing units of the present invention are finished and habitable units, and not simply blocks made up of panels. The present units as described are preferably units of residential housing used in connection with, among others, apartments, condominiums, student housing, assisted care residences, motels and hotels.
The present construction system comprises a floor/ceiling assembly, which floor/ceiling assembly avoids the redundancy of materials for prior art floors and ceilings of stacked modules by providing a ceiling membrane made from gypsum, for example, attached to the floor joists of a unit in the plant. Another distinction between the present floor/ceiling assembly and the prior art attempts at such assemblies is the extent that the prior art units must be finished on-site versus completion in the factory. Further, the floor/ceiling assembly can be constructed out of building materials that are familiar to a typical manufacturer, in the case of present modular housing, the use of steel and gypsum board. The present floor/ceiling assembly concurrently required the development of a way to be able to finish the underside of the floor/ceiling assembly, while still being able to ship it and erect it at the site without damage to the very finishing completed at the factory.
The floor/ceiling assembly additionally comprises an interconnection assembly to connect the units at the site, which interconnection assembly does not inhibit the pre-finishing of the interior and exterior walls. The floor/ceiling assemblies are interconnected at the site at only strategic interior locations, without the use of welding. This allows the exterior walls to be almost completely finished in the plant rather than at the site. Furthermore, the use of the temporary top assembly as a lifting frame eliminates the need for the conventional steel bands around the exterior shell. These prior art steel bands inhibit the finishing of the exterior walls in the plant since the steel bands tend to dig into and distort any finish in which they come in contact.
The present invention further provides a load-bearing assembly that can accommodate the load pressures of stacked units, thus freeing the exterior walls from this support. The present load-bearing assembly is unlike the prior art as it incorporates tubes that are the supporting structural element themselves, with no involvement of the walls. Engineered vertical steel tubes (pipes), preferably all of one size, are strategically placed around the perimeter of the floor/ceiling system. These tubes provide the bearing strength for loads that result from the stacking of the units. Accordingly, all interior and exterior walls are non-load bearing walls. This allows for the units"" walls to be located wherever they are of most use based solely on the aesthetics and functionality of the desired floor plans.
The present invention further comprises a removable and reusable temporary roof for the protection of the interior of the virtually completely finished manufactured housing unit as it is without a permanent ceiling. The roof is attached to a unit at the same connection points that are used for the vertical connection of the units atop each other at the site. Lifting eyes can be attached to the roof allowing the roof to be used effectively as a lifting device in lieu of other conventional banding or frame techniques. The roof maintains the structural integrity of the unit during the stressful lifting process. This top is temporarily attached to the unit in such a way as to add rigidity to the unit during transit in order offset the stresses of racking and shearing.
The present further comprises a permanent roof assembly for those modules that will make up the top floor of the structure.
Further, the present construction system comprises a stabilization assembly. The stabilization assembly provides a way to effect the erection of the units without damaging the pre-finished units. A free standing, self-supporting hallway/stair assembly can be built at the site before the units are erected. The present multi-story stabilization assembly solves the four problems identified above with the progression of setting the units first, without any stabilizing structure.
(1) Since the stabilization assembly is in place with its supporting structural members already leveled and plumbed, the stabilization assembly acts as an effective guide to which the units are attached
(2) Workers can stand on the stabilization assembly to be in a position to maneuver the units into alignment with each other.
(3) The connections required to attach the units together can be accomplished primarily from the interior of the units. Access to the interiors of the units is facilitated by the walkways as they are already in place at each level. The units that abut the stabilization assembly can be attached directly to the stabilization assembly, such attachments enhancing the stability and strength of the units.
(4) Since walkways and stairs have been built prior to the erection of the units, a greater majority of the exterior surfaces of the units that abut the stabilization assembly can be finished in the plant.
The present construction system can be used during the construction of but a single story structure, but provides numerous efficiencies and benefits when utilized with multi-story structures, more specifically with the construction of structures of at least three stories. This preference of structure stories will be understood by those of skill in the art upon review of the drawings and detailed description.
Further, while the manufactured housing units of the present invention can be built of conventional materials, the present construction system provides numerous efficiencies and benefits when utilized with units that comprise a majority of non-wood and/or non-cement infrastructure, wherein wood and/or cement make up a majority of the infrastructure of conventional units. For example, in a preferred embodiment of the present invention, the manufactured housing units comprise a mainly steel infrastructure. This preference of the material make up of the units will be understood by those of skill in the art upon review of the drawings and detailed description.
One of the benefits of the present system is the ability to xe2x80x9cpre-finishxe2x80x9d more of the unit at the manufacturing plant. While it is understandably difficult to label the present invention as enabling the finishing and completion of considerably more of the housing unit at the manufacturing plant (as opposed to on-site construction) than is presently available, the Applicants believe that the line (of how much more finishing can be completed with the present invention than allowable in the present art). In another attempt to define the abilities of the present invention, the present construction system enables approximately a majority of the unit to be pre-finished at the manufacturing plant, which is not possible in current building techniques save for mobile home construction. The approximately a majority of pre-finishing is preferably related to the amount of exterior finishing of the unit, but can also relate to the amount of interior finishing of the unit, or both combined. This preference of the amount of pre-finishing will be understood by those of skill in the art upon review of the drawings and detailed description.
It is an object of the present invention to overcome the problems of traditional modular construction wherein each modular unit is built with a separate floor and ceiling.
It is a further object of this invention to build manufactured housing units that are capable of stacking one upon another, wherein the floor of an upper unit can be hooked with the ceiling of a complementary lower unit.
Another object of the present invention is to develop manufactured housing units that can be stacked at least three stories high.
It is a further object of the present construction system to overcome the problem of traditional modular construction wherein the lower floors of a multi-story structure require vastly wider vertical members with varying spacing to support the upper floors. Concern about the weight, shear, and wind loads as more floors are added puts greater emphasis on the positioning of the exterior load bearing walls, thus reducing the flexibility in floor plan design.
An object of this invention is to utilize steel in the construction of housing units that are to be stacked over three stores in height, the steel capable of minimizing the amount of welding that is necessary to tie units together.
Yet another object of the present invention to maximize the amount of housing unit construction at the plant, instead of on-site. Presently, most of the exterior finish is not completed until the modules are set at the site because of the typical access required at the site to attach the modules together, both horizontally and vertically. With steel modular construction, this accessibility is even more essential since structural steel members are typically welded together.
Another object of the present invention is to provide a free standing, self-supporting hallway/stair (stabilization assembly) built at the site before the units are erected that would solve the problem of instability in present modular structures being, for example, more than three stories in height.
Yet another object of the present invention is to develop a construction system for manufactured housing units wherein the corridors and stairs are erected before the units are set.
These and other objects, features and advantages of the present invention will become more apparent upon reading the following specification in conjunction with the accompanying drawing figures.